The present invention relates to the clinical evaluation of hearing loss and more particularly to an improved acoustic reflex test which is one of a number of tests of the physical characteristics of the middle ear the results of which provide useful indications of the ear condition.
There are a number of clinical tests based upon the use of a probe or probes which are placed in the ears and where probe tones are used together with appropriate instrumentation to examine the functioning of the elements of the inner ear on a non-contact basis. One test which is being increasingly relied upon for determining certain essential characteristics of ears under test is known as an accoustic reflex test. This test is based upon the fact that the stapedial muscle contracts reflexively when it is subjected to a sufficiently loud stimulus tone. A measurement of the sound level at which this contraction occurs is used as a basis for important conclusions with regard to the ear under test. Known reflex testing uses apparatus requiring test devices on both of the patient's ears.
The improvements of the present method and related apparatus permit the test to be performed using a single probe in one ear only which results in increased test reliability with no reliance upon a bilateral ear response. Additionally, the use of a single probe in one ear provides for a simplified and more easily performed test with the preferred embodiments of the apparatus giving substantially automatic test results. This improved test may be designated as an ipsilateral reflex test. The ipsilateral reflex test method is preferably implemented utilizing time division multiplexing. Use is made of reflex latency which is the delay between the presentation of a stimulus tone to the ear and the subsequent reaction of the stapedious muscle. This inherent delay allows the stimulus tone to be presented and the effect of the muscle reaction to be determined subsequent to the turn-off of the stimulus. In this way, interaction between the stimulus signal and the measuring probe tone signal is eliminated by timing the opening of a gate to the reflex detector so that it occurs after the stimulus tone has been presented and the transients produced by it in the electrical circuit have subsided.
Accordingly, an object of the present invention is to provide an improved method and means for acoustic reflex testing.
Another object of the invention is to provide an improved method and means for acoustic reflex testing using a single probe applied to one ear.
Another object of the invention is to provide an improved acoustic reflex test utilizing the inherent delay observed in the response of the stapedious muscle to a stimulating signal.
Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.